# Subtables won't center within threeparttable

I try to center two subtables of which the second one has a tablenote to add which is why I am using a threeparttable. Unfortunately, I cannot get the second subtable centered on the page, it is always shifted to the left... what am I doing wrong here?

\documentclass[12pt]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage{subcaption}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{multirow}

\begin{document}
\newlength{\myl}
\settowidth{\myl}{Suswasser (methylierte Verbindungen)}

\begin{table}[tbh]
\begin{threeparttable}
\centering
\caption[Short Caption]{Some Caption}
\label{tab:Label}
\begin{subtable}{\textwidth}\centering
\caption{Natürliche Systeme}
\begin{tabular}{p{\myl}l}
\toprule
\multirow{2}{*}{Umgebung} & Fraktionierungsfaktor ($$\varepsilon$$)\\
& ...\\
\midrule
Süßwasser (methylierte Verbindungen) & 39 bis 58\\
Marin (Karbonatreduzierung) & 49 bis 95\\
\bottomrule
\end{tabular}
\end{subtable}

\begin{subtable}{\textwidth}\centering
\caption{Kulturexperimente}
\begin{tabular}{p{\myl}ll}
\toprule
\multirow{2}{*}{Substrat} & \multicolumn{2}{c}{Fraktionierungsfaktor ($$\varepsilon$$)}\\
\cmidrule(l){2-3}
& A & B\\
\midrule
Methanol & 68 bis 77 & 40 bis 54\\
... & 24%\tnote{*}
bis 27 & 10\\
... & 39 & 49\\
... & 55 bis 58 & 55 bis 58\\
... & 44 bis 54 &\\
... & 49 &\\
... & 54 &\\
\bottomrule
\end{tabular}
\end{subtable}
\begin{tablenotes}
\item[*] ... fanden ... für Acetat.
\end{tablenotes}
\end{threeparttable}
\end{table}
\end{document}

• Actually it does, it is subtable which behaves strangely try wrapping the entire subtable in \fbox{...} you'll notice that the box is wider than the lines of the subtable. So the real question is why isn't the contents of the subtable centered inside the width given. – daleif Apr 9 '20 at 12:22
• Although aparently not directly related, threeparttable not working with subcaption(subtable), error: table inside subtable might nevertheless be interesting. – leandriis Apr 9 '20 at 12:27
• The threeparttable environment recognizes (unsurprisingly!) three parts: a caption (generally produced by \caption), a tabular-like environment (e.g, tabular, tabular*, and tabularx), and a tablenotes environment. Note what's not in the list of recognized parts: minipage environments. This matters because subtable and subfigure environments are minipage environments that have been told what to do if they encounter \caption statements. – Mico Apr 9 '20 at 13:16
• So it won't work... Is there an alternative to tablenotes? – Manuel Popp Apr 9 '20 at 13:22

Since Mico pointed out that the threeparttable doesn't recognize minipage environments, I looked for an alternative and found that
{\raggedright\footnotesize\centering My footnote \par}

will look the sames as the tablenotes.
• \raggedright is superfluous. – Zarko Apr 9 '20 at 14:29